The circulatory and neural systems of the tooth enter the tooth at the terminus of each of its roots and extend through a narrow, tapered canal system to a pulp chamber adjacent the crown portion of the tooth. If the pulp tissue becomes diseased, extraction of the tooth can often be avoided by removing the diseased tissue and sealing the canal system in its entirety. Endodontic files and reamers are tapered instruments used to remove the diseased tissue in the root canal by reciprocating and/or rotating the instruments in the canal. Since many root canals are small, curved and calcified, the instruments must be able to withstand the torsional load necessary to enlarge the canal without breaking the instrument thus further complicating the treatment.
Once as much of the diseased material as practicable is removed from the root canal, the canal is sealed closed, typically by reciprocating and/or rotating a condenser instrument in the canal to urge a sealing material such as gutta-percha into the canal. Gutta percha used as a sealing material has a high viscosity and thermoplastic character and since the canals are usually small and curved, it is also desirable to use a condenser instrument which is able to withstand the torsional load necessary to urge the material into the canal without breaking the instrument while at the same time condensing the sealing material without leaving any voids in the canal which may lead to treatment failure.
One of the problems with traditional endodontic instruments used for extirpating and filling a root canal is that the torsional limitations of the instrument are often exceeded resulting in breakage of the instrument. Breakage of the instrument may occur as a result of the inadequate removal of dental chips which are cut from the wall of the root canal. The dental chips may be engaged between the instrument and the root canal wall resulting in friction which may cause excessive torque and thus breakage of the instrument.
Traditional reamers or files contain helical flutes along the working portion which are substantially semi-circular in cross-section, that is, an arc tracing a line transverse to the flute length along the bottom of the flute wall is of substantially uniform radii at all points along the line. This structure is intended to promote advancement of tooth chips and debris up the expanding diameter of the instrument along the spiraling flute away from the tip. However, during the extirpating procedure, the dental chips which are formed may be inadequately removed from the root canal and may be forced into flutes along the instrument between the instrument and the root canal causing damage to the canal walls and/or inadequate or uneven tissue removal. This build up of debris may also lead to increased friction resistance already imposed by contact between the instrument and the canal, which in turn increases the torsional load on the instrument. In many cases, the torsional loads on the instrument exceed the tensile strength of the working portion of the instrument resulting in fracture.
It is therefore an object of the invention to provide an endodontic dental instrument which reduces the friction load on the instrument in the root canal.
It is another object of the invention to provide an endodontic dental instrument having a reduced tendency to break during use.
Still another object of the invention is to provide a condenser instrument which more effectively, introduces and condenses a sealing material into an extirpated root canal.
Yet another feature of the invention is to provide a reamer which more effectively removes damaged or diseased tissue from a root canal, thus decreasing friction during root canal cleaning and extirpation and improving the uniformity of the tissue removal from all affected portions of the canal and its defining wall.